1387572 - Build of mozjemalloc.cpp is failing with --enable-warnings-as-errors (-Werror=uninitialized)

Status: RESOLVED FIXED

(Core :: Memory Allocator, defect)

Description

[Sylvestre Ledru [:Sylvestre]]

With gcc 7
 0:17.20 /usr/bin/g++-7 -std=gnu++11 -o mozjemalloc.o -c  -I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/dist/system_wrappers -include /root/firefox-gcc-last/config/gcc_hidden.h -DDEBUG=1 -DMOZ_JEMALLOC_IMPL -DMOZ_HAS_MOZGLUE -I/root/firefox-gcc-last/memory/mozjemalloc -I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/memory/mozjemalloc -I/root/firefox-gcc-last/memory/build -I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/dist/include  -I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/dist/include/nspr -I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/dist/include/nss       -fPIC  -DMOZILLA_CLIENT -include /root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/mozilla-config.h -MD -MP -MF .deps/mozjemalloc.o.pp  -Wall -Wc++11-compat -Wempty-body -Wignored-qualifiers -Woverloaded-virtual -Wpointer-arith -Wsign-compare -Wtype-limits -Wunreachable-code -Wwrite-strings -Wno-invalid-offsetof -Wc++14-compat -Wc++1z-compat -Wimplicit-fallthrough -Wno-error=maybe-uninitialized -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=free-nonheap-object -Wformat -Wformat-overflow=2 -fno-exceptions -fno-strict-aliasing -fno-rtti -fno-exceptions -fno-math-errno -pthread -pipe  -g -freorder-blocks -Os -fno-omit-frame-pointer  -Werror -Wno-unused-function -fdiagnostics-color  /root/firefox-gcc-last/memory/mozjemalloc/mozjemalloc.cpp
 0:17.20 In file included from /root/firefox-gcc-last/memory/mozjemalloc/mozjemalloc.cpp:308:0:
 0:17.20 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void extent_tree_szad_remove(extent_tree_t*, extent_node_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_r_s.extent_node_s::link_szad.extent_node_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21        | (((uintptr_t) (a_node)->a_field.rbn_right_red) & ((size_t)1))); \
 0:17.21                                          ^~~~~~~~~~~~~
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void extent_tree_ad_remove(extent_tree_t*, extent_node_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_r_s.extent_node_s::link_ad.extent_node_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void extent_tree_szad_insert(extent_tree_t*, extent_node_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_i_s.extent_node_s::link_szad.extent_node_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void extent_tree_ad_insert(extent_tree_t*, extent_node_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_i_s.extent_node_s::link_ad.extent_node_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void arena_run_tree_remove(arena_run_tree_t*, arena_chunk_map_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_r_s.arena_chunk_map_s::link.arena_chunk_map_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void arena_avail_tree_insert(arena_avail_tree_t*, arena_chunk_map_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_i_s.arena_chunk_map_s::link.arena_chunk_map_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void arena_avail_tree_remove(arena_avail_tree_t*, arena_chunk_map_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_r_s.arena_chunk_map_s::link.arena_chunk_map_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void arena_chunk_tree_dirty_remove(arena_chunk_tree_t*, arena_chunk_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_r_s.arena_chunk_s::link_dirty.arena_chunk_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void arena_chunk_tree_dirty_insert(arena_chunk_tree_t*, arena_chunk_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_i_s.arena_chunk_s::link_dirty.arena_chunk_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h: In function 'void arena_run_tree_insert(arena_run_tree_t*, arena_chunk_map_t*)':
 0:17.21 /root/firefox-gcc-last/memory/mozjemalloc/rb.h:97:41: error: 'rbp_i_s.arena_chunk_map_s::link.arena_chunk_map_s::<unnamed struct>::rbn_right_red' is used uninitialized in this function [-Werror=uninitialized]

Comment 1

[Sylvestre Ledru [:Sylvestre]]

Attachment: Bug 1387572 - Silent the -Wuninitialized warning

Review commit: https://reviewboard.mozilla.org/r/165040/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/165040/

Comment 2

[Mike Hommey [:glandium]]

Sorry it's taking too long, but I want to be very careful here, this might actually hide a real problem, so I need to dig in some more.

Comment 3

[Mike Hommey [:glandium]]

Comment on attachment 8893962 [details]
Bug 1387572 - Silent the -Wuninitialized warning

https://reviewboard.mozilla.org/r/165040/#review177216

::: memory/mozjemalloc/moz.build:29
(Diff revision 1)
>      CXXFLAGS += ['-Wno-unused-function']
>  
>  if CONFIG['_MSC_VER']:
>      CXXFLAGS += ['-wd4273'] # inconsistent dll linkage (bug 558163)
>  
> +SOURCES['mozjemalloc.cpp'].flags += ['-Wno-error=uninitialized']

Okay, after carefully reviewing the code, those uninitialized warnings are benign. But there's only one source file in this directory, so no need to apply the flag specifically to this source file only (plus, if we ever add new files, we'll go with unified sources anyways, so the flag would need to be applied globally anyways).

Comment 4

[Sylvestre Ledru [:Sylvestre]]

Comment on attachment 8893962 [details]
Bug 1387572 - Silent the -Wuninitialized warning

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/165040/diff/1-2/

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5f06e9d7c0d3
Silent the -Wuninitialized warning r=glandium

Comment 6

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/5f06e9d7c0d3